Precision 3-Wall Scribes

Precision 3-Wall Scribes

A simple template guarantees a perfect fit.

by Brad Holden

Fitting a countertop between two side walls and a back wall is one of the most challenging installations you will ever face. Experienced cabinetmakers can do this with ease by marking and scribing straight to the countertop, but they have years of experience. I take a more roundabout approach, but it’s virtually goof-proof.

I prefer to make a template of the opening and rout my top to match. This prevents trimming too much from any side, which would create a gap that can’t easily be repaired. I’ll show you a simple method for making this template using a kitchen desktop that butts against a cabinet, a side wall and a back wall as an example. I installed this desktop with no backsplash. If you intend to install a backsplash, you don’t need a precise scribe on the back edge.

Materials

You’ll need a piece of plywood or MDF slightly smaller than the countertop opening—about 1/4 in. less at each side and the back is sufficient. This board will be your template’s base and will rest on top of the base cabinets or wall cleats. You’ll also need three guide boards of any 1/4-in.-thick material. Cut them about 4 in. wide. Make two a couple inches longer than the countertop’s depth and one a few inches shorter than the countertop’s width.

Make the Template

Lay the template base on top of the cabinets or cleats and temporarily secure it with a couple of screws (Photo 1). Position one guide board on either the left or right end and push it up against the side and back wall (Photo 2). Next, you’ll need a washer whose rim is big enough to span the widest gap between the wall and the guide board. Put your pencil tip in the washer’s hole and draw a line on the guide board, letting the washer follow the wall’s contour (Photo 3). Clamp the guide board to your workbench, and use a belt sander to sand down to the line (Photo 4). Check the fit against the wall. When you’ve got a snug fit, screw the guide board to the template (Photo 5). Repeat the same steps on the guide boards on the other side and on the back. Cut the back guide board so it fits between the two side guide boards.

Photo 1: Three-wall scribes are tricky because both ends and the back of the countertop all have to fit snugly. My technique removes most of the difficulty by starting with a loose-fitting template base. I’ll scribe three guide boards, one for each wall, and screw them to the template base.

Photo 2: Position the first guide board on the template base by sliding it up against both the side and back wall. It must be long enough to overhang the front of the template base by a couple of inches.

Photo 3: Along the side and back wall, mark a scribe line on the guide board using a pencil and a small washer. The washer follows any bumps or curves in the wall.